一种矩形微米流道的加工与流量测定

介绍了一种比较成熟的矩形微米流道(微槽道)加工工艺,利用厚胶光刻工艺在硅片上制备胶模板,进而在该模板上用高分子聚合物PDMS(Polydimethylsiloxane,聚二甲基硅氧烷)制作了微米量级的微槽道(高、宽范围20~100μm),对制备的微槽道的几何精确度进行了20×100倍放大显微观测,对其流量特性进行了实验测定.实验结果与泊肃叶理论公式(NS方程的管流表达式)相对比,可以看到在微米量级的矩形微流道中,泊肃叶公式仍然适用.     

Measurement of nonlinear mechanical properties of PDMS elastomer

This paper presents the measurement of the nonlinear mechanical properties of polydimethylsiloxane (PDMS) elastomer based on the mixing ratio of base polymer to curing agent. Strip-type PDMS samples with different mixing ratios were prepared using a simple coating, curing, and cutting process. A cyclic uniaxial tension test with a fixed magnitude of applied strain and a single-pull-to-failure tension test were performed with a micro-tensile tester at room temperature.Our new finding is that when the PDMS is mixed with excessive curing agent, stress softening occurs and residual strain exists in cyclic tension tests when the magnitude of the applied strain increases. For the PDMS-05 samples, in which the mixing ratio of base polymer to curing agent was 5 to 1, there were large differences in the stresses for the same strain level under loading and unloading during the first cycle with a 100% fixed strain amplitude, but the softening effect of the stress in the PDMS dropped rapidly starting from the second cycle.Nonlinear mechanical Neo-Hookean, third-order Mooney, and second-order Ogden models of three different PDMS films were computed from the stress-strain data. The results showed that all models were preferable for the small strain region of PDMS compared with other models. In the nonlinear, large strain region, only the second-order Ogden model properly described the mechanical behavior of the PDMS, while the Neo-Hookean and third-order Mooney-Rivlin models were too stiff or flexible in the measurement range. The bulk modulus of PDMS increased with the amount of curing agent in it. Therefore, the second-order Ogden model is preferable for analyzing the PDMS structure over the entire measurement range. This could provide reasonable mechanical models of PDMS for rapid computational prototyping and for designing active and passive components from PDMS.     

Fabrication and application of silicon-reinforced PDMS masters

A new molding process is developed in this work to generate a silicon (Si)-reinforced polydimethylsiloxane (PDMS) master of a 4 in wafer size using an SU-8 mold. The reinforced PDMS master is applied to pattern a conducting polymer, poly-3-hexylthiophene (P3HT), which is normally dissolved by a non-polar solvent. PDMS is usually patterned by a molding process, in which PDMS is first coated on and then peeled off from a rigid mold. However, in the new molding process, the Si-reinforced PDMS master is rigid but the SU-8 mold is flexible, and the SU-8 mold is first placed on and then peeled off from the rigid PDMS master. In such a way, a reinforced PDMS master of a size as large as a 4 in wafer can be produced. Meanwhile, a new way of obtaining free-standing, large SU-8 structures is presented. PDMS swells when it gets exposed to non-polar solvents. This swelling makes PDMS not suitable for patterning materials, which are usually dissolved by non-polar solvents, e.g., P3HT. In this work, we demonstrate that, with the reinforcement of a Si plate, the swelling effect in generating this specific type of materials is much reduced, and good patterns can be produced.     

用硅橡胶膜生物反应器系统选育高性能酿酒酵母

应用硅橡胶膜生物反应器的发酵-渗透汽化耦合功能,进行长期封闭循环发酵,使酵母在这种特定环境下完成适应性自然进化,从而获得优势的突变株。以工业安琪酵母ADY为原始菌株,进行每一轮500h的封闭循环发酵,在发酵终点取菌悬液做平板筛菌,分离出遗传约200代的相对强势的新菌株,再转移新菌株进行同样的发酵和终点筛选实验。如此的发酵-筛选-转移实验共进行了3轮。试验结果表明:ADY遗传超过600代的菌株S33,在500h封闭循环发酵残液配制的培养基条件下,表现出了明显的环境适应性遗传优势,其细胞生长速率、产物乙醇的比生成速率和糖转化率都相对原种菌ADY分别提高了约71.8%、53.6%和52.7%。     

新型硅橡胶复合膜用于分离干红葡萄酒的研究

利用一种自行研制的新型的PDMS平板复合膜对12%vol的"云南红"全汁干型红葡萄酒(2003年酿,国宴供酒)进行渗透汽化脱醇实验,并用气相色谱法对膜上渗余液和膜下冷凝液进行定性和定量分析.在反应罐温度30℃,采用一级冷凝,温度-30℃,渗透池下游保持绝压在真空泵的极限真空度0.1MPa的实验条件下,干红葡萄酒经过8h渗透汽化脱醇后获得了酒精含量为5%vol左右的膜上渗余液和39%vol左右的膜下冷凝液.实验结果发现,新型PDMS平板复合膜对葡萄酒的乙醇及其风味物质表现出了良好的选择分离性能和机械性能.通过一系列分析得知:渗透汽化膜对乙醇的通透量极大;对风味物质的选择性大小为醇类＞酯类,且碳原子数越多,选择性越大.实验表明,渗透汽化膜用于分离干红葡萄酒具有良好的效果,可以预见将其应用于生产低醇葡萄酒和高度的白兰地是可行的.     

受约高分子PDMS链构型的热力学性质的研究

采用统计力学方法,将长链ＰＤＭＳ分子作为一个约束在圆柱体内的小体系进行了处理,利用计算机进行模拟ＰＤＭＳ链的动态过程和处理矩阵连乘,坐标转换,得出受约有限长度高分子链的配合函数表达式及熵的表达式。这为进一步研究多链体系的热 性质提供一种方法。     

Recent advances in the rheooptical characterization of silicon-containing networks

Recent advances in the various theories of strain-birefringenece of polymer networks are presented. The classical theories as well as the more advanced models are outlined together with some recent theoretical results on poly (dimethylsiloxane). Reference to work on other Si-containing polymers is made. The problems of intermolecular correlations occurring in polymer networks and their effect on the observed optical properties are discussed with reference to the optical-configuration parameter. Conclusions report areas of current research.This review was presented at the Second International Topical Workshop, Advances in Silicon-Based Polymer Science.     

Novel catalytic membranes for selective reactions

A survey is given of the potentials of a new kind of catalytic membranes consisting of a catalyst that is immobilised in a dense polymer matrix. When homogeneous, catalytically active complexes are occluded, these membranes constitute a new way of heterogenation. In the case of solid state catalysts, these composite membranes can improve the activity of the catalyst by changing sorption or by allowing experimental set-ups in which solvents become redundant. This revised version was published online in June 2006 with corrections to the Cover Date.     

基于PDMS金属可调谐光栅的制备工艺研究

分别利用直接法和间接法,制备了基于PDMS(聚二甲基硅氧烷)基底的金属可调谐光栅。由于在金属举离过程中PDMS遇丙酮溶液溶胀,导致直接法在机械调谐过程中光栅严重断裂,而利用间接法可以克服此问题。利用PDMS高弹性的特点,通过控制PDMS的纵、横向拉伸程度,对光栅周期进行连续、任意调谐,可获得预定的目标周期。     

Epoxidation of olefines with PDMS membranes containing zeolite occluded manganese diimine complexes

A new composite catalyst for selective epoxidation of olefins with tert-butyl hydroperoxide (tBHP) is reported. The catalyst contains manganese diimine complexes (cis-Mn bis-2,2′-Bipyridyl), occluded within a NaY zeolite, in turn incorporated in a polydimethylsiloxane membrane (cis-[Mn(bpy)₂]²⁺-NaY-PDMS). The three-step synthesis consists of a Mn²⁺exchange of NaY, ligand sorption to form cis-[Mn(bpy)₂]²⁺-NaY and incorporation of the latter in a PDMS membrane. The major differences between [Mn(bpy)₂]²⁺-NaY as such and occluded in PDMS are observed in the sorption and catalytic characteristics. With the membrane system, the use of a solvent becomes obsolete. Whereas optimal cyclohexene oxidation with [Mn(bpy)₂]²⁺-NaY occurs with hydrogen peroxide in acetone, tBuOOH proves to be a better oxidant for [Mn(bpy)₂]²⁺-NaY-PDMS. The reactions in batch and fed-batch reactors are discussed. A simple regeneration procedure, monitored by FT-IR spectroscopy is proposed.